Flight safety is the first priority of airlines, followed by in-flight comfort and operating costs. Another constraint occurs today with the environment: reduction of impacts in terms of noise for the local residents and emission of pollutants.
Currently, descent trajectories generally terminate at constant slope at the time of landing so as to be compatible with the landing means which are materially defined with a constant slope setting (or “Glide slope” as it is known). These trajectories are compatible with all aeroplanes a priori and furthermore make it possible to maintain an appropriate speed for landing. FIGS. 1a and 1b present two examples of approach trajectories according to the known art. The first exemplary approach trajectory, presented in FIG. 1a, comprises a high-altitude descent segment 101, a series of intermediate geometric segments 102 (related to compliance with altitude and speed constraints for the end of the descent) and an approach segment 103 making it possible to stabilize the aeroplane on the runway axis 104 and according to a final approach plane at constant slope 105. This approach segment generally begins in the prior art with a deceleration leg 106. The second exemplary approach trajectory, presented in FIG. 1b, is a recent advance making it possible to dispense with this deceleration leg 106 in the approach segment 103. This type of approach is known by the term CDA for Continuous Descent Approach. Each of these profiles integrates the speed profile matched to the configuration extensions (slats, flaps, undercarriage) desired for the landing.
However, the final segment has a very low slope α, generally of the order of 3°, imposed by the customary landing procedures. This induces an approach trajectory that is close to the ground for quite some time, this being detrimental for the local residents as regards noise. Moreover, maintaining a constant low slope with an approach speed suited to the aeroplane and to the runway imposes an increase in the thrust generating at one and the same time noise, overconsumption and pollutants.